Quote:
Originally Posted by Wayne Doenges
What if you used a servo that will turn CW or CCW without stops? You could use a piece of tubing to match the servo output and the flow control knob.
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Not sure of this year's rules regarding servos. (CAN you use stronger ones THIS season, or continuous rotation servos? You couldn't in previous years.)
Bear in mind that the kit regulators take a LOT torque to turn. Probably way too much for the basic kit servo.
Now you CAN easily make a servo in software with a pressure regulator, a window motor, a 10-turn potentiometer, and TWO pressure transducers (1 for output, 1 for SYSTEM pressure, to make sure you CAN reach it before trying).
In addition to a simple closed loop servo routine in software, you also need to do a few other things:
(a) put both software limits to the pot AND a mechanical friction/slip clutch between the motor and the pot/regulator set, to keep from breaking either one should the motor or software go crazy and attempt to turn it too far in either direction.
(b) monitor the full system pressure as well, to disable the servo routine when the system has insufficient pressure. Otherwise, you will "polarize" the servo wide open, trying to get it to a setting you simply can't reach.
But there are simpler methods.
Example - Create a Buffered Supply Tank, at any programmable pressure.
Use a center-blocked valve (or a pair of kit valves), two flow regulators, a pressure transducer, one Clippard tank, and software. Software is similar to the compressor routine. In this case though, whenever it is out of range EITHER way, pulse one or the other valve coil to either fill or drain the tank until it reaches the desired pressure.
One flow regulator controls the tank FILL rate (NEARLY wide open), while the other controls the BLEED-OFF (probably a fairly low setting, to prevent TOO much air waste from a user's "setting indecisions"
). A software variable now determines the tank's desired "set" pressure, and it "automagically tracks it".
Simpler: Monitor the cylinder's pressure with a transducer. When the cylinder reaches the desired force, just cut off its supply! (Again, use a center-plugged [center-off] valve.)
FYI, a center plugged valve is one of the order options for valve parts in the familiar KoP SMC SY3000 series. See the SMC datasheets for more info.
Does this make sense?
- Keith